/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jca.endpoint;

import java.lang.reflect.Method;

import javax.resource.ResourceException;
import javax.resource.spi.ApplicationServerInternalException;
import javax.resource.spi.UnavailableException;
import javax.resource.spi.endpoint.MessageEndpoint;
import javax.resource.spi.endpoint.MessageEndpointFactory;
import javax.transaction.Transaction;
import javax.transaction.TransactionManager;
import javax.transaction.xa.XAResource;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.BeanNameAware;
import org.springframework.lang.Nullable;
import org.springframework.transaction.jta.SimpleTransactionFactory;
import org.springframework.transaction.jta.TransactionFactory;
import org.springframework.util.Assert;

/**
 * Abstract base implementation of the JCA 1.7
 * {@link javax.resource.spi.endpoint.MessageEndpointFactory} interface,
 * providing transaction management capabilities as well as ClassLoader
 * exposure for endpoint invocations.
 *
 * @author Juergen Hoeller
 * @since 2.5
 * @see #setTransactionManager
 */
public abstract class AbstractMessageEndpointFactory implements MessageEndpointFactory, BeanNameAware {

        /** Logger available to subclasses. */
        protected final Log logger = LogFactory.getLog(getClass());

        @Nullable
        private TransactionFactory transactionFactory;

        @Nullable
        private String transactionName;

        private int transactionTimeout = -1;

        @Nullable
        private String beanName;


        /**
         * Set the XA transaction manager to use for wrapping endpoint
         * invocations, enlisting the endpoint resource in each such transaction.
         * <p>The passed-in object may be a transaction manager which implements
         * Spring's {@link org.springframework.transaction.jta.TransactionFactory}
         * interface, or a plain {@link javax.transaction.TransactionManager}.
         * <p>If no transaction manager is specified, the endpoint invocation
         * will simply not be wrapped in an XA transaction. Check out your
         * resource provider's ActivationSpec documentation for local
         * transaction options of your particular provider.
         * @see #setTransactionName
         * @see #setTransactionTimeout
         */
        public void setTransactionManager(Object transactionManager) {
                if (transactionManager instanceof TransactionFactory) {
                        this.transactionFactory = (TransactionFactory) transactionManager;
                }
                else if (transactionManager instanceof TransactionManager) {
                        this.transactionFactory = new SimpleTransactionFactory((TransactionManager) transactionManager);
                }
                else {
                        throw new IllegalArgumentException("Transaction manager [" + transactionManager +
                                        "] is neither a [org.springframework.transaction.jta.TransactionFactory} nor a " +
                                        "[javax.transaction.TransactionManager]");
                }
        }

        /**
         * Set the Spring TransactionFactory to use for wrapping endpoint
         * invocations, enlisting the endpoint resource in each such transaction.
         * <p>Alternatively, specify an appropriate transaction manager through
         * the {@link #setTransactionManager "transactionManager"} property.
         * <p>If no transaction factory is specified, the endpoint invocation
         * will simply not be wrapped in an XA transaction. Check out your
         * resource provider's ActivationSpec documentation for local
         * transaction options of your particular provider.
         * @see #setTransactionName
         * @see #setTransactionTimeout
         */
        public void setTransactionFactory(TransactionFactory transactionFactory) {
                this.transactionFactory = transactionFactory;
        }

        /**
         * Specify the name of the transaction, if any.
         * <p>Default is none. A specified name will be passed on to the transaction
         * manager, allowing to identify the transaction in a transaction monitor.
         */
        public void setTransactionName(String transactionName) {
                this.transactionName = transactionName;
        }

        /**
         * Specify the transaction timeout, if any.
         * <p>Default is -1: rely on the transaction manager's default timeout.
         * Specify a concrete timeout to restrict the maximum duration of each
         * endpoint invocation.
         */
        public void setTransactionTimeout(int transactionTimeout) {
                this.transactionTimeout = transactionTimeout;
        }

        /**
         * Set the name of this message endpoint. Populated with the bean name
         * automatically when defined within Spring's bean factory.
         */
        @Override
        public void setBeanName(String beanName) {
                this.beanName = beanName;
        }


        /**
         * Implementation of the JCA 1.7 {@code #getActivationName()} method,
         * returning the bean name as set on this MessageEndpointFactory.
         * @see #setBeanName
         */
        @Override
        @Nullable
        public String getActivationName() {
                return this.beanName;
        }

        /**
         * Implementation of the JCA 1.7 {@code #getEndpointClass()} method,
         * returning {@code} null in order to indicate a synthetic endpoint type.
         */
        @Override
        @Nullable
        public Class<?> getEndpointClass() {
                return null;
        }

        /**
         * This implementation returns {@code true} if a transaction manager
         * has been specified; {@code false} otherwise.
         * @see #setTransactionManager
         * @see #setTransactionFactory
         */
        @Override
        public boolean isDeliveryTransacted(Method method) throws NoSuchMethodException {
                return (this.transactionFactory != null);
        }

        /**
         * The standard JCA 1.5 version of {@code createEndpoint}.
         * <p>This implementation delegates to {@link #createEndpointInternal()},
         * initializing the endpoint's XAResource before the endpoint gets invoked.
         */
        @Override
        public MessageEndpoint createEndpoint(XAResource xaResource) throws UnavailableException {
                AbstractMessageEndpoint endpoint = createEndpointInternal();
                endpoint.initXAResource(xaResource);
                return endpoint;
        }

        /**
         * The alternative JCA 1.6 version of {@code createEndpoint}.
         * <p>This implementation delegates to {@link #createEndpointInternal()},
         * ignoring the specified timeout. It is only here for JCA 1.6 compliance.
         */
        @Override
        public MessageEndpoint createEndpoint(XAResource xaResource, long timeout) throws UnavailableException {
                AbstractMessageEndpoint endpoint = createEndpointInternal();
                endpoint.initXAResource(xaResource);
                return endpoint;
        }

        /**
         * Create the actual endpoint instance, as a subclass of the
         * {@link AbstractMessageEndpoint} inner class of this factory.
         * @return the actual endpoint instance (never {@code null})
         * @throws UnavailableException if no endpoint is available at present
         */
        protected abstract AbstractMessageEndpoint createEndpointInternal() throws UnavailableException;


        /**
         * Inner class for actual endpoint implementations, based on template
         * method to allow for any kind of concrete endpoint implementation.
         */
        protected abstract class AbstractMessageEndpoint implements MessageEndpoint {

                @Nullable
                private TransactionDelegate transactionDelegate;

                private boolean beforeDeliveryCalled = false;

                @Nullable
                private ClassLoader previousContextClassLoader;

                /**
                 * Initialize this endpoint's TransactionDelegate.
                 * @param xaResource the XAResource for this endpoint
                 */
                void initXAResource(XAResource xaResource) {
                        this.transactionDelegate = new TransactionDelegate(xaResource);
                }

                /**
                 * This {@code beforeDelivery} implementation starts a transaction,
                 * if necessary, and exposes the endpoint ClassLoader as current
                 * thread context ClassLoader.
                 * <p>Note that the JCA 1.7 specification does not require a ResourceAdapter
                 * to call this method before invoking the concrete endpoint. If this method
                 * has not been called (check {@link #hasBeforeDeliveryBeenCalled()}), the
                 * concrete endpoint method should call {@code beforeDelivery} and its
                 * sibling {@link #afterDelivery()} explicitly, as part of its own processing.
                 */
                @Override
                public void beforeDelivery(@Nullable Method method) throws ResourceException {
                        this.beforeDeliveryCalled = true;
                        Assert.state(this.transactionDelegate != null, "Not initialized");
                        try {
                                this.transactionDelegate.beginTransaction();
                        }
                        catch (Throwable ex) {
                                throw new ApplicationServerInternalException("Failed to begin transaction", ex);
                        }
                        Thread currentThread = Thread.currentThread();
                        this.previousContextClassLoader = currentThread.getContextClassLoader();
                        currentThread.setContextClassLoader(getEndpointClassLoader());
                }

                /**
                 * Template method for exposing the endpoint's ClassLoader
                 * (typically the ClassLoader that the message listener class
                 * has been loaded with).
                 * @return the endpoint ClassLoader (never {@code null})
                 */
                protected abstract ClassLoader getEndpointClassLoader();

                /**
                 * Return whether the {@link #beforeDelivery} method of this endpoint
                 * has already been called.
                 */
                protected final boolean hasBeforeDeliveryBeenCalled() {
                        return this.beforeDeliveryCalled;
                }

                /**
                 * Callback method for notifying the endpoint base class
                 * that the concrete endpoint invocation led to an exception.
                 * <p>To be invoked by subclasses in case of the concrete
                 * endpoint throwing an exception.
                 * @param ex the exception thrown from the concrete endpoint
                 */
                protected void onEndpointException(Throwable ex) {
                        Assert.state(this.transactionDelegate != null, "Not initialized");
                        this.transactionDelegate.setRollbackOnly();
                        logger.debug("Transaction marked as rollback-only after endpoint exception", ex);
                }

                /**
                 * This {@code afterDelivery} implementation resets the thread context
                 * ClassLoader and completes the transaction, if any.
                 * <p>Note that the JCA 1.7 specification does not require a ResourceAdapter
                 * to call this method after invoking the concrete endpoint. See the
                 * explanation in {@link #beforeDelivery}'s javadoc.
                 */
                @Override
                public void afterDelivery() throws ResourceException {
                        Assert.state(this.transactionDelegate != null, "Not initialized");
                        this.beforeDeliveryCalled = false;
                        Thread.currentThread().setContextClassLoader(this.previousContextClassLoader);
                        this.previousContextClassLoader = null;
                        try {
                                this.transactionDelegate.endTransaction();
                        }
                        catch (Throwable ex) {
                                logger.warn("Failed to complete transaction after endpoint delivery", ex);
                                throw new ApplicationServerInternalException("Failed to complete transaction", ex);
                        }
                }

                @Override
                public void release() {
                        if (this.transactionDelegate != null) {
                                try {
                                        this.transactionDelegate.setRollbackOnly();
                                        this.transactionDelegate.endTransaction();
                                }
                                catch (Throwable ex) {
                                        logger.warn("Could not complete unfinished transaction on endpoint release", ex);
                                }
                        }
                }
        }


        /**
         * Private inner class that performs the actual transaction handling,
         * including enlistment of the endpoint's XAResource.
         */
        private class TransactionDelegate {

                @Nullable
                private final XAResource xaResource;

                @Nullable
                private Transaction transaction;

                private boolean rollbackOnly;

                public TransactionDelegate(@Nullable XAResource xaResource) {
                        if (xaResource == null && transactionFactory != null &&
                                        !transactionFactory.supportsResourceAdapterManagedTransactions()) {
                                throw new IllegalStateException("ResourceAdapter-provided XAResource is required for " +
                                                "transaction management. Check your ResourceAdapter's configuration.");
                        }
                        this.xaResource = xaResource;
                }

                public void beginTransaction() throws Exception {
                        if (transactionFactory != null && this.xaResource != null) {
                                this.transaction = transactionFactory.createTransaction(transactionName, transactionTimeout);
                                this.transaction.enlistResource(this.xaResource);
                        }
                }

                public void setRollbackOnly() {
                        if (this.transaction != null) {
                                this.rollbackOnly = true;
                        }
                }

                public void endTransaction() throws Exception {
                        if (this.transaction != null) {
                                try {
                                        if (this.rollbackOnly) {
                                                this.transaction.rollback();
                                        }
                                        else {
                                                this.transaction.commit();
                                        }
                                }
                                finally {
                                        this.transaction = null;
                                        this.rollbackOnly = false;
                                }
                        }
                }
        }

}